Air carrier First Officer reported an EGPWS sink rate warning; an unstable approach and firm landing.

Narrative

Flight from ZZZ to ZZZZ started late due to a maintenance issue. I arrived later with a report of XA:00 under 2hrs call out from crew scheduling due to the crew would have timed out. Ground operation; climb and cruise was uneventful. FO A and I left for break after takeoff and returned to the flight deck the last 4.5hrs of the flight. Looking back the errors started the last 1hr 10mins of flight into ZZZZ. First officer B had the first wake up call since he was PF. After he arrived into the flight deck; I briefed him on aircraft position. As we're waiting for the captain; quite some time had passed but didn't realize FO B didn't wake up the captain after he left the bunk. At this point it's about 45mins to landing and we were given our initial descent. The captain made his way up quickly. PF started briefing; but kept getting interrupted with ATC clearances. FO A and I kept repeating the clearances due to the communication difficulties from ATC to both the PF and PM. (During the debrief; I don't recall the briefing card being used or if the brief was ever completed which would have helped to address all the threats into ZZZZ). Now below 10;000ft; we were being vectored on and off the arrival to create spacing. FO B was getting behind so the captain was assisting with the airspeed. Something unusual that was questioned in the debrief was during the descent and when asked by ATC to slow; the thrust lever was held and speed brakes were deployed which was causing us to get slow -10 below target airspeed multiple times. Check path and airspeed was called out or you have the speed brakes out" multiple times. There seemed to be a lack of situational awareness with the automation. We were then cleared cleared to descend to 6000 on the arrival again with a clearance clearing us for the approach with another airspeed reduction. We all agreed to set 4100 with the clearance from the approach plate. Approach button was armed but then we got another clearance to immediately level at 6000 and a left turn outside of ZZZZZ on the arrival due to catching up on the traffic again. The captain quickly completed the read back and completed the heading with the airspeed and assisted the PF. We were then cleared for the approach again. Established on the ILSXXL; the aircraft is getting configured but the thrust levers and speed brakes are still out quite a bit making us slow. I do not recall the winds but below 1000 it felt windy but I think it was mostly self induced due to the PF overcorrecting exceeding 1200FPM multiple times. Around 300feet; as I'm watching the PFD and considering a go around; I believe the airplane aural warning sink..rate came on. Someone called correcting and continue but the time it registered and trying to remember if we have to call a go around at this point we were in the landing flare with a very hard; firm landing. It was within the touchdown zone. At the gate during the debrief--there were quite a few discrepancies; disagreements; none receptiveness and uncertainty. The next day to the airport we brought up the approach to landing phase again and it felt as if inputs weren't being respected to what we should have done better and how we all could learn from this."